fix(backend): use searchTitle in YTM URL (was using raw title with release suffix)

YTM search used `title` directly, so "recognize - Single" was searched on
YouTube Music instead of "recognize" — causing no YTM results and falling
through to the less reliable YouTube search cascade.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/lib/ytdlp.js

@@ -181,7 +181,7 @@ async function downloadTrack({ jobId, artist, rawArtist, albumArtist, title, alb
 
   const YTM_SONGS_PARAM = 'EgWKAQIIAWoKEAkQBRAKEAMQBA%3D%3D';
   // Use original (raw) artist for YTM URL — better ranking since channel is in original language
-  const ytmQuery = `${rawArtist || mainArtist} - ${title}${albumQuerySuffix}`;
+  const ytmQuery = `${rawArtist || mainArtist} - ${searchTitle}${albumQuerySuffix}`;
   const ytmUrl = `https://music.youtube.com/search?q=${encodeURIComponent(ytmQuery)}&params=${YTM_SONGS_PARAM}`;
   const expectedAudio = path.join(dir, `${fileBase}.${CONFIG.audioFmt}`);
   const hasAudio = () => fs.existsSync(expectedAudio);